Guide wire with embolic filtering attachment

ABSTRACT

A separate deliverable embolic protection device filter that attaches to a helical coil at a distal end of a conventional guide, for use in a blood vessel when an interventional procedure is being performed to capture any embolic material which may be created and released into the bloodstream during the procedure. The device includes a filter assembly with a proximal end and a distal end, and a guide wire connector attached to the distal end of the filter assembly. The guide wire connector is able to couple with the helical coil of the guide wire. A restraining sheath placed over the filter assembly in a coaxial arrangement maintains the filter assembly in a collapsed position and delivers the filter assembly separately to the helical coil of the guide wire, and then the guide wire connector is joined to the helical coil. Alternatively, the guide wire can include a rotatable coil section forming a portion of the distal tip coil on the guide wire which is adapted to be coupled to the filter assembly. This arrangement allows the filter assembly to be rotatably mounted onto the guide wire.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. Ser. No. 10/260,718, filed Sep. 30, 2002,U.S. Pat. No. 7,331,973, issued Feb. 19, 2008. The contents of which arehereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to filtering devices used, forexample, when an interventional procedure is being performed in astenosed or occluded region of a body vessel to capture embolic materialthat may be created and released into the vessel during the procedure.The present invention is more particularly directed to a separatelydeliverable embolic filter assembly having an expandable basket andfilter that can be attached to the distal tip coil of a conventionalguide wire via a guide wire connector.

Numerous procedures have been developed for treating occluded bloodvessels to allow blood to flow without obstruction. Such proceduresusually involve the percutaneous introduction of an interventionaldevice into the lumen of the artery, usually by a catheter. One widelyknown and medically accepted procedure is balloon angioplasty in whichan inflatable balloon is introduced within the stenosed region of theblood vessel to dilate the occluded vessel. The balloon dilatationcatheter is initially inserted into the patient's arterial system and isadvanced and manipulated into the area of stenosis in the artery. Theballoon is inflated to compress the plaque and press the vessel wallradially outward to increase the diameter of the blood vessel, resultingin increased blood flow. The balloon is then deflated to a small profileso that the dilatation catheter can be withdrawn from the patient'svasculature and the blood flow resumed through the dilated artery. Asshould be appreciated by those skilled in the art, while theabove-described procedure is typical, it is not the only method used inangioplasty.

Another procedure is laser angioplasty which utilizes a laser to ablatethe stenosis by super heating and vaporizing the deposited plaque.Atherectomy is yet another method of treating a stenosed body vessel inwhich cutting blades are rotated to shave the deposited plaque from thearterial wall. A vacuum catheter is usually used to capture the shavedplaque or thrombus from the blood stream during this procedure.

In the procedures of the kind referenced above, abrupt reclosure mayoccur or restenosis of the artery may develop over time, which mayrequire another angioplasty procedure, a surgical bypass operation, orsome other method of repairing or strengthening the area. To reduce thelikelihood of the occurrence of reclosure and to strengthen the area, aphysician can implant an intravascular prosthesis for maintainingvascular patency, commonly known as a stent, inside the artery acrossthe lesion. The stent can be crimped tightly onto the balloon portion ofthe catheter and transported in its delivery diameter through thepatient's vasculature. At the deployment site, the stent is expanded toa larger diameter, often by inflating the balloon portion of thecatheter.

The above non-surgical interventional procedures, when successful, avoidthe necessity of major surgical operations. However, there is one commonproblem which can become associated with all of these non-surgicalprocedures, namely, the potential release of embolic debris into thebloodstream that can occlude distal vasculature and cause significanthealth problems to the patient. For example, during deployment of astent, it is possible that the metal struts of the stent can cut intothe stenosis and create particles of plaque that can travel downstreamand lodge somewhere in the patient's vascular system. Pieces of plaquematerial are sometimes generated during a balloon angioplasty procedureand are released into the bloodstream. Additionally, while completevaporization of plaque is the intended goal during laser angioplasty,sometimes particles are not fully vaporized and enter the bloodstream.Likewise, not all of the emboli created during an atherectomy proceduremay be drawn into the vacuum catheter and, as a result, may enter thebloodstream as well.

When any of the above-described procedures are performed in the carotidarteries, the release of emboli into the circulatory system can beextremely dangerous and sometimes fatal to the patient. Debris carriedby the bloodstream to distal vessels of the brain can cause cerebralvessels to occlude, resulting in a stroke, and in some cases, death.Therefore, although cerebral percutaneous transluminal angioplasty hasbeen performed in the past, the number of procedures performed has beensomewhat limited due to the justifiable fear of an embolic strokeoccurring should embolic debris enter the bloodstream and block vitaldownstream blood passages.

Medical devices have been developed to attempt to deal with the problemcreated when debris or fragments enter the circulatory system followingvessel treatment utilizing any one of the above-identified procedures.One approach which has been attempted is the cutting of any debris intominute sizes which pose little chance of becoming occluded in majorvessels within the patient's vasculature. However, it is often difficultto control the size of the fragments which are formed, and the potentialrisk of vessel occlusion still exists, making such a procedure in thecarotid arteries a high-risk proposition.

Other techniques include the use of catheters with a vacuum source whichprovides temporary suction to remove embolic debris from thebloodstream. However, as mentioned above, there can be complicationsassociated with such systems if the catheter does not remove all of theembolic material from the bloodstream. Also, a powerful suction couldcause trauma to the patient's vasculature.

Another technique which has had some success utilizes a filter or trapdownstream from the treatment site to capture embolic debris before itreaches the smaller blood vessels downstream. The placement of a filterin the patient's vasculature during treatment of the vascular lesion canreduce the presence of the embolic debris in the bloodstream. Suchembolic filters are usually delivered in a collapsed position throughthe patient's vasculature and then expanded to trap the embolic debris.Some of these embolic filters are self expanding and utilize arestraining sheath which maintains the expandable filter in a collapsedposition until it is ready to be expanded within the patient'svasculature. The physician can retract the proximal end of therestraining sheath to expose the expandable filter, causing the filterto expand at the desired location. Once the procedure is completed, thefilter can be collapsed, and the filter (with the trapped embolicdebris) can then be removed from the vessel. While a filter can beeffective in capturing embolic material, the filter still needs to becollapsed and removed from the vessel. During this step, there is apossibility that trapped embolic debris can backflow through the inletopening of the filter and enter the bloodstream as the filtering systemis being collapsed and removed from the patient. Therefore, it isimportant that any captured embolic debris remain trapped within thisfilter so that particles are not released back into the body vessel.

Some prior art expandable filters vessel are attached to the distal endof a guide wire or guide wire-like member which allows the filteringdevice to be steered in the patient's vasculature as the guide wire ispositioned by the physician. Once the guide wire is in proper positionin the vasculature, the embolic filter can be deployed to captureembolic debris. The guide wire can then be used by the physician todeliver interventional devices, such as a balloon angioplasty dilatationcatheter or a stent delivery catheter, to perform the interventionalprocedure in the area of treatment. After the procedure is completed, arecovery sheath can be delivered over the guide wire using over-the-wireor rapid exchange (RX) techniques to collapse the expanded filter forremoval from the patient's vasculature.

Some prior art filtering devices utilize a construction in which theexpandable filter is permanently affixed to the guide wire. When theexpandable filter is permanently attached to the guide wire, the devicemay have added stiffness and therefore may lose some “front-line”capability, which is the ability to negotiate the often tortuous anatomythrough which it is being delivered. The stiffness of a combinedexpandable filter and guide wire may possibly prevent the device fromreaching the desired target area within the patient's vasculature. Also,in such a design, it is possible for the deployed filtering portion ofthe device to rotate or move with the guide wire in the event that theguide wire is rotated by the physician during usage. As a result, thereis a possibility that the deployed filtering portion of the device couldscrape the vessel wall possibly causing trauma. Therefore, when such afiltering device is utilized, it is important that the proximal end ofthe guide wire remains fixed since rotation could possible betransmitted to the deployed filtering portion of the device. However,since a physician normally delivers interventional devices along theguide wire after the filter portion has been deployed, some manipulationof the guide wire takes place an it may be difficult to prevent at leastsome rotation at the proximal end of the guide wire.

Some prior art filtering devices utilize a separate filtering assemblywhich can be delivered over the guide wire and attaches to a specialfitting located near the distal end of the guide wire. However, thesefiltration devices require the fitting to be placed near the distal endof the guide wire which can possibly hinder the ability to steer theguide wire and reach the target area in the patient's vasculature. Theseparticular filter systems also require additional manufacturingprocedures to properly mount the fitting onto the steerable guide wire.As such, the presence of the fitting near the distal end of the guidewire may cause unwanted problems during delivery of the guide wirethrough the patient's vasculature.

Therefore, what has been needed is a filtering device that can beattached to the distal end of a guide wire after the guide wire has beeninitially deployed into the target region of a patient. The filterportion of the device should be easy to deliver, easily attachable tothe guide wire and should eliminate the need for special fittings to beplaced on the guide wire. Also, it would be beneficial if the filteringportion is rotatably mounted onto the guide wire to prevent the deployedfiltering portion from rotating and possible scraping the vessel wallonce deployed. The present invention satisfies these and other needs.

SUMMARY OF THE INVENTION

The present invention provides a separately deliverable filter assemblyhaving an expandable basket (also referred to as a “cage”) and a filterelement that can be attached to the distal coil tip of a conventionalguide wire. In use, the present invention is designed to capture embolicdebris created during the performance of a therapeutic interventionalprocedure, such as a balloon angioplasty or stenting procedure, or otherunwanted particulates entrained in the fluid of a body vessel. Thepresent invention allows the physician to deliver the guide wire with“front-line” capabilities to steer through the tortuous anatomy, whilestill being able to provide filtering protection in the form of aseparately deliverable attachment.

An embolic filtering device made in accordance with the presentinvention utilizes a filter assembly having an expandable basket capableof being disposed for traveling over the guide wire. The filter assemblyhas a proximal end and a distal end with a guide wire connector coupledto the distal end. Once in proper position, the guide wire connector isable to be coupled to the distal tip coil of the guide wire. Theexpandable basket can be made from a self-expanding material, forexample, nickel-titanium alloy (NiTi), and may include struts capable ofexpanding from a collapsed position or configuration having a firstdelivery diameter to an expanded or deployed position or configurationhaving a second implanted diameter. The filter element may be made froman embolic-capturing material and is attached to the expandable basketsuch that it moves with the basket between the collapsed and deployedpositions. Guide wire connectors of the present invention are easilyadapted for attachment on a number of different configurations of filterassemblies and can be attached to a variety of different guide wires.

The guide wire used in the present invention may include steerable guidewires having distal tip coils which allow the guide wire connector to bescrewed onto the tip coil. Also, any guide wire with coil spacing largeenough to allow a guide wire connector having spring-loaded tabs toengage the tip coils may be implemented. Another guide wire that may beused in the present invention is found in U.S. Pat. No. 6,132,389 issuedto Cornish et al., which discloses a proximally tapered guide wire tipcoil. One embodiment of the present invention uses a variation of thecoil tip design found in Cornish et al. patent, where the proximallytapered guide wire tip coil is stretched somewhat to create a matchingcoil to which the guide wire connector is attached.

In one particular embodiment of the present invention, the guide wireconnector associated with the filter assembly is a connection coilcapable of being screwed onto the helical coil of the guide wire. When aguide wire with a proximally tapered distal tip coil is used, theconnection coil may have a similar pitch to the tip coil on the guidewire.

In another embodiment of the present invention, the guide wire connectorassociated with the filter assembly includes at least one spring-loadedtab adapted to grasp a distal tip coil on the guide wire. In anotherparticular embodiment, a pair of spring-loaded tabs are used to graspthe distal tip coil of the guide wire to lock the filter assembly at thedistal end of the guide wire. In this regard, the spring-loaded tabs aredesigned to latch onto the coils of the guide wire. The connector alsomay include three or more spring-loaded tabs designed to grasp and lockonto the guide wire tip coil.

In use, the present invention is able to capture embolic debris or otherparticulates entrained in the fluid of a blood vessel of a patientduring, for example, an interventional procedure such as an angioplastyprocedure or stenting procedure. Initially, a guide wire having a distaltip coil would be inserted into the body vessel and steered into thetarget area. Once the guide wire is delivered across the area oftreatment, the filter assembly, which has a guide wire connectordisposed at its distal end, would be delivered along the guide wireuntil it reaches the distal end of the guide wire. The guide wireconnector would then be secured to the helical coil of the guide wire.The type of connection made at the distal coil tip will depend on thetype of guide wire connector associated with the filter assembly. Inorder to transfer the filter assembly along the guide wire, theexpandable basket of the filter assembly is maintained in a collapsedposition by a delivery sheath which extends co-axially over the filterassembly. Alternatively, a rapid exchange delivery sheath could be usedin which an offset lumen is utilized to maintain the filter assembly ina collapsed position. The delivery sheath, along with the collapsedfilter assembly, can be delivered over the guide wire until the guidewire connector of the filter assembly locks the filter assembly to theguide wire. The filter assembly can be placed in its expanded positionsimply by retracting the delivery sheath proximally, allowing theexpandable basket to self deploy. As the struts of the basket expandradially, so does the filter element which will now be deployed withinthe body vessel to collect embolic debris and particles that may bereleased into the bloodstream as the physician performs theinterventional procedure. The delivery sheath can be removed from theguide wire to allow an interventional device to be delivered over theguide wire to the area of treatment. After the procedure is completed,the interventional device is removed from the guide wire and a recoverysheath can be delivered along the guide wire and over the filterassembly to return it to its collapsed position. The guide wire, alongwith the sheath and filter assembly, can be then removed from thepatient.

When an overlapping connection coil is utilized, the delivery sheath maybe rotated in order to interconnect the connecting coil onto the helicalcoil of the guide wire. It is contemplated that the guide wire could berotated itself or simultaneously rotated with the delivery sheath toscrew the connecting coil onto the tip coil of the guide wire. Inanother embodiment in which the connector includes spring-loaded tabs,the delivery sheath can be moved in a distal direction forcing thespring-loaded tabs to grasp one of the coils of the guide wire. It iscontemplated that once the sheath delivers the filter assembly to thedistal end of the guide wire, the guide wire could be moved in aproximal direction while holding the delivery sheath steady to force thespring-loaded tabs into a recess formed between adjacent coils.

In an alternative embodiment, the distal tip coil of the guide wire mayinclude a rotating portion mounted onto the guide wire and used forattachment to the filter assembly. In this manner, once the guide wireconnector is attached to the rotating coil section of the guide wire,the filter assembly will be free to spin or rotate relative to the guidewire. The filter assembly will remain stationary in a deployed positionwithin the patient even if the guide wire is rotated by the user. Inanother particular embodiment, the guide wire includes a rotating coilsection rotatably mounted on the guide wire. The rotating coil sectioncan be placed between a pair of stationary coil sections which cooperateto form a composite tip coil.

It is to be understood that the present invention is not limited by theembodiments described herein. Alternatively, the present invention canbe used in arteries, veins, and other body vessels. By altering the sizeof this design, it also may be suitable for peripheral and neurologicalapplications. Other features and advantages of the present inventionwill become more apparent from the following detailed description of theinvention, when taken in conjunction with the accompanying exemplarydrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in cross-section and partiallyfragmented, of a guide wire with an embolic filter assembly embodyingfeatures of the present invention.

FIG. 2 is an elevational view of one embodiment of a filter assembly,similar to the one shown in FIG. 1, having a connection coil disposed ona distal end.

FIG. 3 is an elevational view of another embodiment of a filter assemblyhaving a pair of spring-loaded tabs disposed on the distal end.

FIG. 4 is an elevational view, partially in cross section, of aconventional guide wire including a helical coil.

FIG. 5 is an enlarged view of a distal portion of a guide wire having aproximally tapered stretched helical coil.

FIG. 6 is an elevational view, partially in cross-section of oneembodiment of a filter assembly in a collapsed position and including aconnection coil attached to the helical coil of a guide wire.

FIG. 7A is an elevational view, partially in cross-section of oneembodiment of a filter assembly in a collapsed position and includingspring-loaded tabs attached to the helical coil of a guide wire.

FIG. 7B is an elevational view, partially in cross-section of anotherembodiment of a filter assembly including spring-loaded tabs whichextend proximally for attachment to the helical coil of a guide wire.

FIG. 7C is an elevational view, partially in cross-section of anotherembodiment of a filter assembly including spring-loaded tabs whichextend proximally for attachment to the helical coil of a guide wire.

FIG. 8 is an elevational view, partially in cross-section, of a filterassembly in a collapsed position attached to the helical coil of a guidewire, within a body vessel at a downstream location from an area to betreated.

FIG. 9 is an elevational view, partially in cross-section, similar tothat shown in FIG. 8, wherein the filter assembly is deployed in itsexpanded position within the body vessel for filtering purposes.

FIG. 10A is an elevational view, partially in cross-section, of the endan expandable basket of a filter assembly (shown without the filtermember) in a deployed position and attached to a rotating coil sectionforming a portion of the distal tip coil of a guide wire.

FIG. 10B is an elevational view of the distal end of filter assemblywhich can be permanently mounted to the rotating coil section forming aportion of the distal tip coil of a guide wire.

FIG. 11 is an elevational view of one particular embodiment of a filterassembly, similar to the one shown in FIG. 10, which can be used inaccordance with the present invention.

FIG. 12 is an elevational view of a distal portion of a guide wirehaving a rotating coil section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings, in which like reference numerals representlike or corresponding elements in the drawings, FIG. 1 illustrates oneparticular embodiment of an embolic filtering device 20 incorporatingfeatures of the present invention. This embolic filtering device 20 isdesigned to capture, for example, embolic debris which may be createdand released into a body vessel during an interventional procedure. Theembolic filtering device also can be used to filter any unwantedparticles entrained in the fluid of a body vessel, such as largemicrospheres of a therapeutic agent which may be released into thevessel during a localized drug delivery procedure.

The embolic filtering device 20 includes an expandable filter assembly22 having a self-expanding basket or cage 24 and a filter element 26attached thereto. The filter assembly 22 has a proximal or first end 28and a distal or second end 30, and in the embodiment shown in FIG. 1,there is a first sleeve or collar 32 disposed on the first end and asecond sleeve or collar 34 disposed on the second end. The first andsecond sleeves 32 and 34 can be both cylindrically shaped. A guide wireconnector 36 can be attached to the second end 30 of the filter assembly22, and as shown in FIG. 1, the guide wire connector is directlyattached to the distal or second sleeve 34. In this figure, theexpandable filter assembly 22 is engaged with an elongated (solid orhollow) cylindrical tubular shaft, such as a steerable guide wire 40having a distal tip coil 42. The guide wire 40 has a proximal end (notshown in FIG. 1) which extends outside the patient and is delivered bythe physician across a target area in the patient's vasculature. Arestraining or delivery sheath 44 delivers the filter assembly 22separately along the guide wire 40 in order to maintain the expandablefilter assembly 22 in its collapsed position until it is ready to bedeployed within the patient's vasculature. In the particular embodimentshown in FIG. 1, the physician may rotate the delivery sheath 44 toattach the guide wire connector 36 to the helical tip coil 42 of theguide wire 40. Then, once connected to the guide wire 40, the expandablefilter assembly 22 can be deployed by the physician by simple retractingthe delivery sheath 44 proximally to expose the expandable filterassembly. Once the restraining sheath is retracted, the self-expandingbasket 24 immediately begins to expand within the body vessel, causingthe filter element 26 to expand as well.

One embodiment of the embolic filtering device is shown in FIG. 2 inwhich the guide wire connector is a connection coil 50 disposed on thesecond sleeve 34. The connection coil 50 is able to be screwed onto thehelical tip coil 42 of the guide wire 40. In the embodiment of FIG. 2,the expandable filter assembly 22 includes a tubular member or shaft 52connected to the first and second ends 28 and 30 and is slidablydisposed upon the guide wire 40. One of these first or second ends 28should include a slip connection to allow the basket to elongate when itcollapses and shorten when it expands. Alternatively, tubular member 52could be fixed at both ends 28 and 30 and be made from a coil that canlengthen and shorten as needed. This same structure can be applied toany of the other embodiments described herein. This shaft 52 helps tomaintain the integrity of the filter assembly as the filter assembly isbeing retracted by a recovery sheath. The filter assembly 22 anddelivery sheath 44 are separately rotatable on the guide wire 40 duringdelivery to the distal end of the guide wire. Even when the connectioncoil 50 is coupled to the helical coil 42 of the guide wire 40, thefilter assembly 22 can be separately rotatable independent from theguide wire. This can be accomplished by having the filter assembly 22rotate independently of the second sleeve 34, which would be joined tothe guide wire 40 through the coil connector 50.

Referring now to FIG. 3, another embodiment is shown where the connector36 is a spring-loaded tab 54, and more specifically a pair ofspring-loaded tabs 54 disposed opposite one another on the second sleeve34. In operation, the spring-loaded tabs on the distal end 30 of thefilter assembly 22 would catch one of the coils of the tip coil 42 ofthe guide wire 40. It is also contemplated that there could be one ormore spring-loaded tabs disposed on the second sleeve 34 that wouldcatch the coil of the guide wire 40. One advantage of usingspring-loaded tabs 54 is that the guide wire connector does not have tobe rotated to be attached to the tip coil of the guide wire.

The embolic filtering device 20 can be constructed with a conventionalguide wire 40 having a tip coil 42 disposed at a distal end. Referringnow to FIG. 4, a conventional guide wire 40 is shown. The guide wire 40depicted in FIG. 4 has an elongate core member 60 with a proximalsection 62 and a distal section 64. This embodiment shows the distalsection 64 of the guide wire 40 having at least one distally taperedportion 66. A flexible body member or helical coil 42 is disposed aroundthe distal section 64, and the helical coil has a proximal end 68 and adistal end 70. In this embodiment the helical coil 42 has a relativelyconstant diameter from the proximal end 68 to the distal end 70. Thehelical coil 42 is attached to the guide wire 40 at both the proximalend 68 and the distal end 70. In the event that the spacing betweencoils is too tight, i.e., the tip is too stiff and will not bend throughtortuous anatomy, the physician can simply apply a small amount ofproximal force to portion 68 to cause a portion of the tip coil toexpand longitudinally, thus creating space between coils which enhancethe ability of the spring-like tabs to catch and hold onto the tip coil.

In another embodiment however, the helical coil 42 has a taperedproximal end 72, shown in FIG. 5, which is similar to the proximallytapered coil found in U.S. Pat. No. 6,132,389 issued to Cornish et al. Atapered angle 74 of the tapered proximal end 72 is the angle the tangentto the tapered section 66 makes with the longitudinal axis of thehelical coil 40, can be from about 0.1 to 10° and preferably about 0.5to 2°. The distal end 70 of the helical coil 42 typically has an outerdiameter approximately equal to the nominal outer diameter of theproximal section 62 of the elongate core member 60. Details of a guidewire having a proximally tapered helical coil can be found in theCornish et al. patent. The tapered proximal end 72 shown in FIG. 5differs from the proximal tapered helical coil found in the Cornish etal. patent in that the tapered proximal end is somewhat stretched,forming spaces or gaps 76 in between individual coils. This embodimentallows the connection coil to screw onto the stretched proximal taperedhelical coil and lock in place within the gaps 76. When using aproximally tapered helical coil and a connection coil 50 on the filterassembly 22, it may be preferred that both have a similar pitch. Theincreased gap between adjacent coils again helps to enhance the abilityof the spring-loaded tabs to latch onto a coil(s).

Referring now to FIG. 6, the embodiment of the present invention whichuses a connection coil 50 disposed on the second sleeve 34 to lock thefilter assembly into place is shown in greater detail. This figure alsoshows the filter assembly 22 being held in a collapsed position insidethe delivery sheath 44. In order to connect the filter assembly 22 tothe helical coil 42 of the guide wire 40, the delivery sheath is rotatedclockwise, screwing the connection coil 50 onto the helical coil 42. Itis also contemplated that the guide wire could be rotatedcounter-clockwise or rotated simultaneously with the sheath to screw theconnection coil 50 onto the helical coil 42. Once the filter assembly 22is secured onto the guide wire 40, the delivery sheath 44 can then bewithdrawn, allowing the filter assembly to expand.

Now referring to FIG. 7A, the present invention is shown in which thefilter assembly 22 includes spring-loaded tabs 54 disposed on the secondsleeve 34 and locked into place on the tapered proximal end 72 of thehelical coil 42. The spring-loaded tabs 54 are caught inside the helicalcoil 42, however, the spring-loaded tabs may be designed to grab aroundthe outside of the helical coil. In order to hook the spring-loaded tabs54 into or around the helical coil 42, the delivery sheath 44 may haveto be forced or pushed proximally into the helical coil of the guidewire. It is also contemplated that the guide wire 40 may be forced orpulled distally into the spring-loaded tabs 54 to hook the spring-loadedtabs onto the helical coil. As with the embodiment shown in FIG. 6, oncethe spring-loaded tabs 54 are secured to the guide wire 40, the deliverysheath 44 may then be withdrawn so the filter assembly may expand.

An alternative embodiment of the filter assembly of FIG. 7A is shown inFIG. 7B. In this particular embodiment, the filter assembly includesspring-loaded tabs 54 disposed on the second sleeve 34 which extendproximally rather than distally, as is shown in FIG. 7A. In thisparticular embodiment, the spring-loaded tabs 54 will lock into place onthe helical coil 42. This particular embodiment may help to ease theinsertion of the tabs 54 into the helical coil 42 and also may enhancethe holding power of this connection. Another alternative design isshown in FIG. 7C in which the spring-loaded tabs 54 are again disposedto extend proximally from the second sleeve 34. Both of the embodimentsshown in FIGS. 7B and 7C have spring-loaded tabs facing proximally whichwill tend to wedge tighter once the filter assembly 22 comes in contactwith the helical coil 42. Additionally, these particular embodiments mayhelp to hold the filter assembly 22 tighter onto the guide wire via thehelical coil 42 in the event that the filter assembly 22 is ever caughtin the patient's anatomy and the guide wire is pulled proximally.

In FIGS. 8 and 9, the embolic filtering device 20 is shown within anartery 80 or other body vessel of the patient. This portion of theartery 80 has an area of treatment 82 in which, for example,atherosclerotic plaque 84 has built up against the inside wall 86 of theartery 80. In operation, the physician would first insert the guide wire40 into the vasculature of the patient, positioning the distal section64 of the guide wire across the area of treatment 82 with the distal endand helical coil 42 located downstream from the area of treatment. Next,the delivery sheath 44 delivers the filter assembly 22 separately alongthe guide wire 40 in order to maintain the expandable filter assembly 22in its collapsed position. The physician manipulates the sheath 44and/or the guide wire 40 to join the connector 36, in this embodimentthe connection coil 50, to the helical coil 42. Once the filter assembly22 is joined to the helical coil 42, the expandable filter assembly 22is expanded by the physician by simply retracting the delivery sheath 44proximally to expose the expandable filter assembly. Once therestraining sheath is retracted, the self-expanding cage 24 immediatelybegins to expand within the body vessel, causing the filter element 26to expand as well. By attaching the filter assembly 22 to the guide wireafter the guide wire has been delivered to the area of treatment 82, thephysician is able to deliver the guide wire with “front-line”capabilities and is still able to obtain embolic protection as aseparate attachment.

Referring now to FIG. 9, the embolic filtering device 20 is shown in itsexpanded position within the patient's artery 80. Any embolic debris 90created during an interventional procedure will be released into thebloodstream and will enter the filter assembly 22 located downstreamfrom the area of treatment 82. Once the procedure is completed and theembolic debris 90 is collected in the filter element 26, the filterassembly 22 can be collapsed by a recovery sheath 44 which slides overthe filter assembly, allowing the embolic filter device 20 to be removedfrom the patient's vasculature.

When the filtering assembly 22 is collapsed by the recovery sheath,there is a possibility that the proximal end of the filter assembly maymove somewhat distally as the end of the recovery sheath contacts theassembly. This may occur, for example, in the embodiment shown in FIG.1, since the proximal end of the filter assembly is not physicallyattached to the guide wire, but rather is slidably disposed on the guidewire. This may not occur if the expandable basket has sufficient axialstiffness. However, when a filter assembly such as the one in FIG. 1 isutilized, a recovery sheath having a large inner diameter may be used tocapture a greater portion of the proximal end of the filter assembly. Asa result, the recovery sheath may help to prevent the proximal end frommoving distally as the sheath slides over the filter assembly. Anotherway to prevent the end from moving is to utilize a tubular member orshaft, such as is shown in the embodiments of FIGS. 2 and 3. The tubularshaft 52 provides axial rigidity which prevents the proximal end of thefilter assembly from being pushed distally as a recovery sheath extendsover the filter assembly. Again, the distal connection of the tubularshaft 52 and basket should be a sliding fit in order to allow the basketto open and close. The tubular shaft 52 used in accordance with theembodiments of FIGS. 2 and 3 is just one example of adding stiffness ina longitudinal direction to enhance the ability of the filter assemblyto be collapsed by the recovery sheath.

Referring now to FIGS. 10-12, another embodiment of the embolicfiltering device 20 is shown as it is rotatably mounted onto thespecially adapted guide wire 92. In this particular embodiment, theguide wire 92 has a composite tip coil 94 including a rotating coilsection 96 which is rotatably mounted to the core of the guide wire 92.This rotating coil section is disposed between a proximal coil section98 and a distal coil section 100 which are both fixed to the core of theguide wire. The proximal coil section 98 and the distal coil section 100act as stop fittings to maintain the rotating coil segment 96longitudinally fixed there between, yet allows the rotating coil segmentto rotate relative to the guide wire. The proximal coil section 98 anddistal coil section 100, along with the rotating coil section 96,cooperatively form a composite tip coil which can be bent to a J-shapedconfiguration, or other configuration, as is well-known in the art, toaid in the steering of the guide wire through the patient's anatomy.

The guide wire connector 36 is adapted to engage and attach to therotating coil section 96 which forms the composite tip coil 94. Theguide wire connector 36 which can be used in accordance with thisembodiment can be either the connection coil described above or thespring-loaded tabs described in conjunction with the embodiment of FIG.3.

As can be better seen in FIG. 12, the rotating coil section 96 isdisposed between the proximal coil section 98 and the distal coilsection 100. It should be appreciated that the outer diameter of theproximal coil section 98 may be somewhat smaller than the outer diameterof the rotating coil section 96 to allow the distal end of the filterassembly to extend thereover when the connection to the rotating coilsection is being performed. When the spring-loaded tabs are utilized,the gaps between the coils of the rotating coil section 96 may beincreased to provide gaps which help the tabs to latch onto the coils ofthe rotating coil section.

As can be seen in FIG. 11, the filter assembly 22 may include anobturator 102 made from a soft material such as PEBAX 40D which providesan atraumatic tip to the filter assembly as it is being advanced overthe guide wire within the patient's vasculature. The soft-tippedobturator 102 helps to prevent the distal end of the filter fromscraping the walls of the body vessel as it is being advancedtherethrough. This same type of obturator can be used to in accordancewith any of the other embodiments of the filter assembly used inaccordance with the present invention.

Alternatively, as in shown in FIG. 10B, the distal end of the filterassembly 22 can be soldered directly to the rotating coil section 96 tocreate a one-piece embolic filtering device which can also be usedduring the performance of interventional procedures for capturing anyembolic debris which may be created. If the distal end of the filterassembly is permanently attached to the rotating coil section 96, thenthe filtering assembly would not be able to be delivered separately oncethe guide wire has been steered into the target area in the patient'svasculature, but rather, would move with the distal end of guide wirealong with the delivery sheath which maintains it in its collapsedposition. Such a composite filter/guide wire could be delivered into apatient's vasculature for particulate filtration.

The guide wire connector 36 made in accordance with the presentinvention has been shown as it is connected to the distal sleeve whichforms part of the expandable basket of the filter assembly. However, theguide wire connector also could be formed on the tubular shaft 52 usedin accordance with the embodiments of the filter assemblies of FIGS. 2and 3. It also can be a separate piece which is bonded or otherwiseattached to the distal end of any conventional filtering assembly.Accordingly, the guide wire connector 36 can take on many differentshapes and forms other than those shown in the particular figuresdisclosed herein to perform the same function as that disclosed herein.It should be appreciated that modifications can be made to the guidewire, filter assembly and guide wire connector without departing fromthe spirit and scope of the present invention.

It should be appreciated that the guide wire connectors could be placedon the proximal end of the filter assembly, rather than the distal end.The guide wire connectors are shown attached to the distal most end ofthe filter assemblies in the particular embodiments described herein.However, similar type connectors could be placed on the proximal end ofthe filter assembly without departing from the spirit and scope of thepresent invention.

The expandable basket of the present invention can be made in many ways.One particular method of making the basket is to cut a thin-walledtubular member, such as nickel-titanium hypotube, to remove portions ofthe tubing in the desired pattern for each strut, leaving relativelyuntouched the portions of the tubing which form the structure. Thetubing may be cut into the desired pattern by means of amachine-controlled laser. The tubing used to make the basket couldpossibly be made of suitable biocompatible material, such as springsteel. Elgiloy is another material which could possibly be used tomanufacture the basket. Also, very elastic polymers possibly could beused to manufacture the basket.

The strut size is often very small, so the tubing from which the basketis made may have a small diameter. Typically, the tubing has an outerdiameter on the order of about 0.020-0.040 inches in the unexpandedcondition. Also, the basket can be cut from large diameter tubing.Fittings are attached to both ends of the lased tube to form the finalbasket geometry. The wall thickness of the tubing is usually about 0.076mm (0.001-0.010 inches). As can be appreciated, the strut width and/ordepth at the bending points will be less. For baskets deployed in bodylumens, such as PTA applications, the dimensions of the tubing may becorrespondingly larger. While it is preferred that the basket be madefrom laser cut tubing, those skilled in the art will realize that thebasket can be laser cut from a flat sheet and then rolled up in acylindrical configuration with the longitudinal edges welded to form acylindrical member.

Generally, the tubing is put in a rotatable collet fixture of amachine-controlled apparatus for positioning the tubing relative to alaser. According to machine-encoded instructions, the tubing is thenrotated and moved longitudinally relative to the laser which is alsomachine-controlled. The laser selectively removes the material from thetubing by ablation and a pattern is cut into the tube. The tube istherefore cut into the discrete pattern of the finished struts. Thebasket can be laser cut much like a stent is laser cut. Details on howthe tubing can be cut by a laser are found in U.S. Pat. No. 5,759,192(Saunders), U.S. Pat. No 5,780,807 (Saunders) and U.S. Pat. No 6,131,266(Saunders) which have been assigned to Advanced Cardiovascular Systems,Inc.

The process of cutting a pattern for the strut assembly into the tubinggenerally is automated except for loading and unloading the length oftubing. For example, a pattern can be cut in tubing using a CNC-opposingcollet fixture for axial rotation of the length of tubing, inconjunction with CNC X/Y table to move the length of tubing axiallyrelative to a machine-controlled laser as described. The entire spacebetween collets can be patterned using the CO₂ or Nd:YAG laser set-up.The program for control of the apparatus is dependent on the particularconfiguration used and the pattern to be ablated in the coding.

A suitable composition of nickel-titanium which can be used tomanufacture the strut assembly of the present invention is approximately55% nickel and 45% titanium (by weight) with trace amounts of otherelements making up about 0.5% of the composition. The austenitetransformation temperature is between about 0° C. and 20° C. in order toachieve superelasticity at human body temperature. The austenitetemperature is measured by the bend and free recovery tangent method.The upper plateau strength is about a minimum of 60,000 psi with anultimate tensile strength of a minimum of about 155,000 psi. Thepermanent set (after applying 8% strain and unloading), is less thanapproximately 0.5%. The breaking elongation is a minimum of 10%. Itshould be appreciated that other compositions of nickel-titanium can beutilized, as can other self-expanding alloys, to obtain the samefeatures of a self-expanding basket made in accordance with the presentinvention.

In one example, the basket of the present invention can be laser cutfrom a tube of nickel-titanium (Nitinol) whose transformationtemperature is below body temperature. After the strut pattern is cutinto the hypotube, the tubing is expanded and heat treated to be stableat the desired final diameter. The heat treatment also controls thetransformation temperature of the basket such that it is super elasticat body temperature. The transformation temperature is at or below bodytemperature so that the basket is superelastic at body temperature. Thebasket is usually implanted into the target vessel which is smaller thanthe diameter of the basket in the expanded position so that the strutsof the basket apply a force to the vessel wall to maintain the basket inits expanded position. It should be appreciated that the basket can bemade from either superelastic, stress-induced martensite NiTi orshape-memory NiTi.

The basket could also be manufactured by laser cutting a large diametertubing of nickel-titanium which would create the basket in its expandedposition. Thereafter, the formed basket could be placed in itsunexpanded position by backloading the basket into a restraining sheathwhich will keep the device in the unexpanded position until it is readyfor use. If the basket is formed in this manner, there would be no needto heat treat the tubing to achieve the final desired diameter. Thisprocess of forming the basket could be implemented when usingsuperelastic or linear-elastic nickel-titanium.

The struts forming the proximal struts can be made from the same or adifferent material than the distal struts. In this manner, more or lessflexibility for the proximal struts can be obtained. When a differentmaterial is utilized for the struts of the proximal struts, the distalstruts can be manufactured through the lazing process described abovewith the proximal struts being formed separately and attached. Suitablefastening means such as adhesive bonding, brazing, soldering, weldingand the like can be utilized in order to connect the struts to thedistal assembly. Suitable materials for the struts include superelasticmaterials, such as nickel-titanium, spring steel, Elgiloy, along withpolymeric materials which are sufficiently flexible and bendable.

The polymeric material which can be utilized to create the filteringelement include, but is not limited to, polyurethane and Gortex, acommercially available material. Other possible suitable materialsinclude ePTFE. The material can be elastic or non-elastic. The wallthickness of the filtering element can be about 0.00050-0.0050 inches.The wall thickness may vary depending on the particular materialselected. The material can be made into a cone or similarly sized shapeutilizing blow-mold technology or dip molding technology. The openingscan be any different shape or size. A laser, a heated rod or otherprocess can be utilized to create to perfusion openings in the filtermaterial. The holes, would of course be properly sized to catch theparticular size of embolic debris of interest. Holes can be lazed in aspinal pattern with some similar pattern which will aid in there-wrapping of the media during closure of the device. Additionally, thefilter material can have a “set” put in it much like the “set” used indilatation balloons to make the filter element re-wrap more easily whenplaced in the collapsed position.

The materials which can be utilized for the restraining sheath can bemade from polymeric material such as cross-linked HDPE. This sheath canalternatively be made from a material such as polyolifin which hassufficient strength to hold the compressed strut assembly and hasrelatively low frictional characteristics to minimize any frictionbetween the filter assembly and the sheath. Friction can be furtherreduced by applying a coat of silicone lubricant, such as Microglide®,to the inside surface of the restraining sheath before the sheath isplaced over the filter assembly. Silicone also can be placed on thefilter material as well.

Further modifications and improvements may additionally be made to thedevice and method disclosed herein without departing from the scope ofthe present invention. Accordingly, it is not intended that theinvention be limited, except as by the appended claims.

1. A method of capturing embolic debris released into a blood vessel ofa patient, comprising: inserting a guide wire having a coil at a distalend into the blood vessel and directing the distal end of the guide wireto a treatment area; slidably mounting a filter assembly having a guidewire connector disposed at one end onto the guide wire, and directingthe filter assembly along the guide wire, wherein the guidewireconnector includes a spring-loaded tab; and forcing the filter assemblyand spring-loaded tab together with the coil of the guide wire, catchingthe spring-loaded tab in between windings of the coil of the guide wire.2. The method of claim 1, further comprising placing a sheath over thefilter assembly to maintain the filter assembly in a collapsed position,and then directing the sheath including the filter assembly over theguide wire until the connector abuts the coil of the guide wire.
 3. Themethod of claim 2, further comprising retracting the sheath to exposethe filter assembly after the connector is coupled to the coil of theguide wire, allowing the filter assembly to form an expanded position.4. The method of claim 3, further comprising fitting the sheath over thefilter assembly and removing the guide wire and sheath from the vessel.5. The method of claim 1, wherein the guide wire connector is disposedat a distal end of the filter assembly.
 6. The method of claim 1,wherein the guide wire connector is disposed at a proximal end of thefilter assembly.